Contact lenses are widely used for correcting defects such as near-sightedness and far-sightedness (myopia and hypermetropia, respectively). Most contact lenses available on the market for correcting myopia or hypermetropia typically have spherical designs, namely, each contact lens having a spherical anterior surface and a spherical posterior surface. Although contact lenses with spherical lens design provide acceptable visual acuity, there are several disadvantages associated with such traditional design. First, a spherical lens design may lead to an inadequate lens fitting on an eye, since human cornea generally has an aspherical surface. Second, a spherical lens design can introduce undesirable spherical aberrations into a lens due to its geometry and thereby decrease visual acuity. By providing a lens surface with asphericity, one may be able to eliminate spherical aberrations. However, by eliminating spherical aberrations of a lens, the optical power profile of a contact lens is inadvertently changed and as such, the apparent optical power at a given aperture (e.g., 4 mm pupil size) of a lens may no longer be the desired and targeted optical power. Such changes in apparent optical powers may greatly hinder a eye-care practitioner to correctly prescribe a contact lens to a patient.
Therefore, there is a need for contact lenses which provide good lens fitting and have controlled lens spherical aberrations.